International Study on Syncope of Uncertain Etiology 2: the management of patients with suspected or certain neurally mediated syncope after the initial evaluation rationale and study design.

STUDY DESIGN Multi-centre, prospective observational study. OBJECTIVES Main objective is to verify the value of implantable loop recorder (ILR) in assessing the mechanism of syncope and the efficacy of the ILR-guided therapy after syncope recurrence. INCLUSION CRITERIA Patients who met the following criteria are included: suspected or definite neurally mediated syncope based on initial evaluation; >/=3 syncope episodes in the last 2 years; severe clinical presentation of syncope requiring treatment initiation in the judgement of the investigator and age >30 years. EXCLUSION CRITERIA Patients with one or more of the following are excluded: carotid sinus syndrome; suspected or definite heart disease and high likelihood of cardiac syncope; symptomatic orthostatic hypotension diagnosed by standing blood pressure measurement; loss of consciousness different from syncope (e.g. epilepsy, psychiatric, metabolic, drop-attack, TIA, intoxication, cataplexy) and subclavian steal syndrome. END-POINTS: The primary end-points are the ECG-documented syncopal events and the syncope recurrences after application of ILR-guided therapy. SAMPLE SIZE AND DURATION: A minimum of 400 patients will be enrolled during an anticipated period of 3 years.